The present invention relates to digital data communication systems and, more particularly, to a novel method for arbitration of collisions in such systems.
It is well known to use bit arbitration to resolve priority conflicts in data transmission systems where several remote, or slave, stations tend to simultaneously transmit a message to a master station. In many data transmission systems where noise and attenuation exist on the transmission medium, contention among communication units is generally resolved by restricting transmission to a single station which is specifically designated by polling and the like techniques. In the event that specific-designation techniques are not used, collisions between transmissions from a plurality of remote-slave stations would normally occur and all of the contending stations would cease transmission before making a second attempt, usually after a random delay, to transmit the message without collision. It will be seen that such techniques reduce the system data rate, as a particular station must either hold its data until polled or must repeat its transmission several times until the message is completely transmitted without collision. It is highly desirable to provide a method for digital data transmission, in a system in which collisions may occur, in such manner that system time is not lost and not even a portion of a message from a successfully-contending remote station need be repeated.